The maximum number of Scrollback lines appears to be 5000. I would like to increase it...
Oh. That limit does seem kind of arbitrary. Also according to [the docs](https://developer.gnome.org/vte/0.48/VteTerminal.html#vte-terminal-set-scrol...) it's legal to pass a negative value for "infinite scrollback" but that won't work since the value is arbitrarily clamped between 0 and 5000.